Author Institution: Department of Zoology, Miami Universit

Barrett, Gary W.

Stueck, Karen L.

The Ohio Journal of Science

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BRIEF NOTECALORIC INGESTION RATE ANDASSIMILATION EFFICIENCY OFTHE SHORT-TAILED SHREW,BLARINA BREVICAUDA1Although several studies have beenconcerned with the bioenergetics of theshort-tailed shrew, Blarina brevicauda(e.g., Pearson, 1947; Morrison et al., 1957;Buckner, 1964; Platt, 1974), only thestudies by Martinsen (1969) and Ran-dolph (1973) permit direct comparisonbetween geographical regions regardingcaloric intake and assimilation efficiencyvalues, i.e., age, weight, diet, and labora-tory conditions were similar for the lattertwo studies. There remains a wide dis-crepancy concerning various energeticvalues for this species.shrews (two male and two female) weremeasured for a 12-day period for eachindividual during the months of Octoberand November, 1972. The shrews weretrapped near Oxford, Ohio, in the earlyfall of 1972. The food consumptionmethod, as outlined by Odum el al.(1962), was used in determination ofenergetic parameters. Shrews were placedon a diet of mealworms (Tenebrio molitor)and all feeding experiments were con-ducted in metabolism cages in order thatfood intake and feces could be measuredseparately. Water was provided ad libi-tum and all experiments were conductedat room temperature (22°-23° C). Thebioenergetics data are summarized intable 1 and all data are expressed asmean =•= standard deviation.Each shrew was weighed daily duringa 12-day study period. The mean weightTABLE 1Bioenergetics of the short-tailed shrew maintained on a diet of mealworms.Shrew*SexM iM2F iF 2XWeight (g)19.99±2.2515.56±0.7515.32±0.5714.51±1.8716.35±2.47Food Intake(Kcal/g live wt/day)1.16=»=0.390.91 ±0.191.18±0.121.13±0.191.09±0.13AssimilationEfficiency (%)88.00±3.3487.79±5.9990.84=1=1.4691.47±1.0089.53±1.90*Data are based on 12 daily measurements for each shrew and areexpressed as mean ± standard deviation.Interestingly, Randolph (1973) hasshown Blarina to differ, according to sea-son of capture, for various laboratory en-ergetic determinations. It is possiblethat these seasonal differences may relateto geographical differences as well. Itwas the objective of our study to quantifythe caloric intake and assimilation ef-ficiency parameters, and to measure andpartially evaluate the bioenergetics of theshort-tailed shrew collected from south-ern Ohio.Mean food (caloric) intake and assimi-lation efficiency of four adult short-tailedManuscript received July 10, 1975, and inrevised form as a note November 6, 1975 (#75-46).for all individuals was 16.35±2.47 g.A mean weight gain of 0.32 ±0.28 g forthe shrews during the course of the feed-ing studies indicates that individualweights did not fluctuate greatly. Thiswas expected of adult animals that chan-nel little assimilated energy into sec-ondary production.Feces and uneaten mealworms werecollected daily. Collected feces weredried to a constant weight at 40° C in avacuum oven. A fecal caloric value of3.35 Kcal/g dry weight, as determinedby Barrett (1969) for the least shrew,Cryptotis parva, was used to determine thecaloric fecal output per day. A caloricequivalent of 2.33 Kcal/g live weight was252G GARY W. BARRETT AND KAREN L. STUECK Vol. 76used for the mealworms (Brisbin, 1966)in computation of daily ingestion rates.The mean daily ingestion rate for the 4animals was 7.95 ±0.17 g live weight foodor 18.51 ±3.80 Kcal. Thus, the shrewsingested approximately 0.49 g live weightfood per gram live weight animal per dayor 1.09 Kcal/g live weight (see table 1).Martinsen (1969), working with 20 gshrews collected from Illinois betweenJuly and December, reports an ingestionrate of approximately 6.0 Kcal/day or0.30 Kcal/g for animals maintained onmealworms at 22°-24° C. Randolph(1973) reports a daily food intake rateof 22.93 Kcal per 20 g adult animal (2.29Kcal/g live weight) for summer-caughtshrews and 18.59 Kcal per animal (1.86Kcal/g live weight) for winter-caughtshrews. These shrews, collected in On-tario, Canada, were measured at 23° Cand fed "shrewburgers" (i.e., mixed por-tions of cereal, hamburger, ground beefliver, and vegetable juice) with a caloricvalue of 6.34 Kcal/g dry weight, a valueenergetically comparable to mealworms(Slobodkin and Richman, 1961).Energy loss through defecation was0.57±0.l7g/day or 1.95 ±0.56 Kcal/day.Thus, mean assimilation efficiency (in-gestion energy-fecal energy/ingestion en-ergy X100) was 89.53 ±1.90% (see table1). The assimilation efficiency found inthis study is approximately equal to thatfound by both Martinsen (1969) andRandolph (1973), regardless of localityor season of capture. It should be noted,however, that difference in diet is an im-portant factor in determining assimila-tion efficiency. For example, Buckner(1964) found that Blarina has an assimi-lation efficiency of 78% when eatinglarch sawfly eonymphs and 92% whenfeeding on canned dog food. Based onthe results of our study, short-tailedshrews exhibit comparable assimilationefficiency values when tested under lab-oratory conditions regardless of seasonor site of capture. Such is not the caseconcerning rate of food intake of southernshrews which exhibited an intermediaterate of food consumption as compared tonorthern individuals. It appears that theenergy needs of the short-tailed shrew aredependent upon variation in the amountof food intake, rather than on variationin assimilation efficiency.—GARY W.BARRETT AND KAREN L. STUECK,Department of Zoology, Miami Uni-versity, Oxford, Ohio 45056.LITERATURE CITEDBarrett, G. W. 1969. Bioenergetics of a cap-tive least shrew, Cryptotis parva. J. Mammol.50: 629-630.Brisbin, I. L., Jr. 1966. Energy-utilizationin a captive hoary bat. J. Mammol. 47: 719-720.Buckner, C. H. 1964. Metabolism, food ca-pacity, and feeding behavior in four speciesof shrews. Can. J. Zool. 42: 259-279.Martinsen, D. L. 1969. Energetics and ac-tivity patterns of short-tailed shrews onrestricted diets. Ecology 50: 505-510.Morrison, P. R., M. Pierce and F. A. Ryser.1957. Food consumption and body weightin the masked and short-tailed shrews. Am.Midi. Nat. 57: 493-501.Odum, E. P., C. E. Connell, and L. B. Daven-port. 1962. Population energy flow of threeprimary consumer components of old-fieldecosystems. Ecology 43: 88-96.Pearson, O. P. 1947. The rate of metabolismof some small mammals. Ecology 28: 127-145.Platt, W. J. 1974. Metabolic rates of short-tailed shrews. Physiol. Zool. 47: 75-90.Randolph, J. C. 1973. Ecological energeticsof a homeothermic predator, the short-tailedshrew. Ecology 54: 1166-1187.Slobodkin, L. B. and S. Richman. 1961.Calories/gm. in species of animals. Nature191: 299.

Brief Note Caloric Ingestion Rate and Assimilation Efficiency of the Short-Tailed Shrew, Blarina Brevicauda

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Brief Note Caloric Ingestion Rate and Assimilation Efficiency of the Short-Tailed Shrew, Blarina Brevicauda

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